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Automotive/Car Won't Start When It's Warm Outside
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Question
Hi Ernie,
Have kind of a strange issue that I haven't seen before and was hoping you could help with. I have a '97 Jetta that seems to never want to turn on when it's been sitting in the sun for a while. Bizarre, right?
Living in Chicago, I would expect the opposite -- the car SHOULD have trouble turning on when it's -20 degrees outside, not when it's 75 and sunny. But just the opposite -- if the car is warm inside when I get in it, it's almost guaranteed to not start. The starter just won't engage. For a while, jiggling the steering column a little while turning the key in the ignition seemed to help, but that only lasted about a week before ceasing to make a difference.
Last summer, I took it to a local auto mechanic chain and they explained to me that it was a "heat sensor" that had gone bad, which at least made sense. $600 later and the return of warm weather, though, still no luck.
I should also mention that the car has never had any overheating or cooling issues once it's running.
Any help or direction would be very appreciated -- thanks in advance Ernie!
There is an intermittently-open circuit somewhere in the starter-enable circuit; this could be in the ignition/start switch itself, or it could be at the starter contactor, or it could even be at the starting motor itself. That early "fix" that appeared to work when you manipulated the steering column does suggest that the ignition/ start switch is a good place to start (pun intended). These switches are subject to a fair bit of mechanical duress, all the more if intended to lock the steering wheel as well, so they are an item that is likely to be replaced during the life times of many cars.
Thermally-related intermittent problems can be tricky to find, and also misleading as to what to expect. Depending on the mechanical configuration of the affected contacts (which may be in a switch or a connector), thermal expansion can either separate two contacts which normally would be expected to be connected together, or it may bring them together while contraction due to cooling will separate them. In the case of your car, the problem would appear to be the former.
From your description of the problem scenario, I would be inclined to check out the ignition/start switch itself, plus take a good look at the related harness and connectors in the steering column at the same time.
One hopes that you will find the replacement of the ignition switch to be much less than you paid for that apparently unnecessary replacement of the "heat sensor". In any case, parts themselves are generally not that pricey.
Good luck ... EGK
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Answers by Expert:
Ernest (Ernie) Kenward
Expertise
The challenges I most enjoy are thoughtful technical questions of a trouble-shooting nature in both electrical, power electronic and mechanical systems, mainly automotive but also machine control and small-machine PLC applications. Please note, however, that I am NOT a walking shop manual! I DO, however, make it a point to have those manuals and other service literature for those vehicles I DO own, and highly recommend that anyone serious about maintenance or modification of their vehicles do the same; MOST of your answers WILL be found there. For that matter, I do NOT go out of my way to acquire shop manuals for any vehicle I do NOT own! That being the case, any general query to me along the lines of "What is the meaning of this code read from the ECU of my 2015 XYZ?" or "Where is the fuse for the windshield washer pump found?" (try your car's electrical distribution panel for a start!) will not go far. What I do offer is a pretty good collection of literature, insights and hands-on experience with 1950s to 1980's Ford products (plus a developing database of information and practice with the Mercedes diesel cars), along with an engineering perspective and the ability to design and implement custom control, electrical and mechanical subsystems for vehicles. For that reason, I am happy to make my thoughts and efforts available to those who are of like mind and/or are seriously making a point of learning about their vehicles. Use the Opportunity to Learn!
Experience
A key skill in my work and hobby pursuits both is STRATEGIC TROUBLESHOOTING. I am a senior instructor in Electrical Engineering Technology at a leading Canadian polytechnic, my areas being Electrical Power and Industrial Control, electrical and electronics design and manufacturing, and AutoCAD and related CAD/CAE software - plus equipment problem-solving and new equipment design and prototyping.
Hobby-wise, I have 30-plus years of experience in auto restoration, mostly in electrical and mechanical systems. Ongoing projects include a 1959 Edsel Corsair, my 1978 Ford E250 class-B motorhome conversion, and the care and upkeep of my Mercedes 300CD.
My vehicles become engineering test beds for electrical and mechanical upgrades as ideas present themselves. This includes the design and production of circuit boards to restore or enhance features for which no OEM replacement parts are obtainable, or where better specifications or reliability can be had via newer concepts. Regarding the E250 RV conversion, I designed and continue to revise a custom power distribution system, managed by a Programmable Controller (PLC); this has made most revisions as easy as uploading new firmware as I develop it.
The "mini" PLC is a powerful device for custom automotive control systems. One good example (there are many) would be the Moeller "Easy Relay"; these offer a wealth of control, monitoring and variable-and-status display options for such projects. A good example project which has worked well is that one for my RV noted above, which has been on the job - revised in firmware only - for a decade now. It is a load management and charging control system to avoid the sulfation-induced early failure that often befalls deep-cycle batteries used in RV power applications. The battery installed in 2003 lasted long enough to more tnan pay for the PLC that contributed to its longer life ... and the PLC will be there for the next battery as well!
Organizations
IEEE - senior member ... past WCC Student Activities;
SME - senior member ... past chair, greater Vancouver chapter chair 318;
Edsel Owners' Club - have served in various capacities on chapter executive during seventies;
have been Power and Driveline resource on the Edsel Owners' Club "E-team" for more than a decade.
Education/Credentials
Graduate of UBC
Awards and Honors
Certificates of appreciation from IEEE and SME for work in student and chapter activities
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